1. Field of the Invention
This invention relates to a strain relief device for use with cables or lines subject to tensive forces, especially cables such as fiber optic cables whose bend radius is constrained.
2. Description of Related Art
The problem of providing adequate protection from external tensive forces upon cables so that the force is essentially reduced to nothing at the termination of the cable or line has been addressed in a number of ways. This protection is necessary in many systems with cabling because there may be fragile and expensive components at the end of the cables. Many strain relief devices of the prior art are too large to be feasibly installed in many systems. For example, strain relief has been achieved by wrapping cables around a mandrel or other cylindrical body. This method, however, becomes impractical when the bend radius of the cable is constrained to be at least a certain minimum. Such bend radius constraints are especially a problem with fiber optic cables, since excessive curvatures may lead to loss of optical quality and strength. In addition, this expedient of the prior art results in an unwieldy and unorganized grouping of cables when more than one cable is involved.
Other strain relief devices of the prior art are application specific in that the means for providing the stress relief is located at the termination of the cable as an integral part of the stress-sensitive component. An example of this type of strain relief device is disclosed in U.S. Pat. No. 3,432,794. In the arrangement shown in the patent, a card frame assembly having rails on the side of the frame is arranged to hold down the cable in a U-shape. Another example of this type of strain relief device is shown in U.S. Pat. No. 3,740,698. In the device described in this latter patent, a housing at the end of a connector is formed with an S-curve section allowing external forces to be absorbed within the configuration of the curve.
Still other strain relief devices are shown in U.S. Pat. Nos. 4,493,467 and 4,744,627 as well as in the IBM Technical Disclosure Bulletin, vol. 20, No. 12, p. 5349. None of the strain relief devices shown in these publications is particularly suitable for use with large numbers of fiber optic cables.